EP 0 856 181 B1 has disclosed a method and a device for evaluating an anesthesia EEG or intensive-care EEG. The anesthesia EEG or intensive-care EEG is classified from EEG curves by means of mathematical-statistical methods. Moreover, artifacts are registered and taken into account for correcting or suppressing classifications.
EP 1 795 122 A1 has disclosed the practice of registering EEG signals and bio-impedance signals. Instances where a bio-impedance threshold is exceeded or the similarity between the signals in the EEG signal and in the bio-impedance signal is/are used for artifact recognition. The bio-impedance analysis can be used to discard EEG signal sections that are subjected to artifacts, or the classification as “awake” can be supported, for example if blinking eyes are identified. This document predominantly relates to artifacts in the facial region.
U.S. Pat. No. 6,731,975 A has disclosed a method for determining the cerebral status of a patient, for example after an anesthetic is administered. To this end, the entropy in the EEG signal and in the combined EEG-EMG signal, and a pure EMG index, are calculated.
It was found that there are a number of triggers for bio-signals, which can modify EEG curves and interfere with a classification of the anesthesia EEG or intensive-care EEG. Volatile anesthetics on the basis of flurane, in particular sevoflurane, should be highlighted since these can trigger seizure potentials with increasing dosage.